Problem: $\dfrac{9}{4} - \dfrac{8}{12} = {?}$
Explanation: $ = {\dfrac{9 \times 3}{4 \times 3}} - {\dfrac{8 \times 1}{12 \times 1}} $ $ = {\dfrac{27}{12}} - {\dfrac{8}{12}} $ $ = \dfrac{{27} - {8}}{12} $ $ = \dfrac{19}{12}$